High solids pigment coating composition

ABSTRACT

A high solids pigmented coating composition is prepared from a curing agent and an ester diol binder which is a mixture of 
     (a) 20-80 mole % of a compound having the general formula: ##STR1## where R 1  represents the group formed by abstraction of the two carboxyl groups from a cycloaliphatic and/or aromatic dicarboxylic acid having 8 to 20 carbon atoms and R 2  and R 3  may be the same or different and represent groups formed by abstraction of the two hydroxyl groups from a divalent alcohol having 2 to .[.12.]. .Iadd.6 .Iaddend.carbon atoms, and m is a number of 1 - 3, and 
     (b) 80-20 mole % of a compound having the general formula: ##STR2## where R 4  represents the group formed by abstraction of the two carboxyl groups from an aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and R 5  and R 6  may be the same or different and represent groups formed by abstraction of the two hydroxyl groups from a divalent alcohol having 2 to .[.12.]. .Iadd.6 .Iaddend.carbon atoms, and n is a number of 1 - 3.

This invention relates to a pigmented coating composition having a highsolids content and prepared from a blend of an ester diol as a binderand a curing agent.

A composition prepared from a diester diol is disclosed in U.S. Pat. No.3,857,817. The dicarboxylic acid disclosed for the preparation of thediester diol is either an aromatic dicarboxylic acid such asterephthalic acid, or an aliphatic dicarboxylic acid. Applicant hasfound now that, if the disclosed composition does not contain a pigment,the hardness and flexibility of the coating are satisfactory. If,however, the disclosed composition contains a pigment, which is oftenthe case, then the hardness or flexibility is not entirely satisfactory.

It is therefore an object of this invention to provide a coatingcomposition of the type described above which has both high flexibilityand high hardness. Another object of the invention is to provide apigmented coating composition prepared from a diester diol havingimproved hardness and flexibility characteristics.

In accordance with this invention, the foregoing objects and others areaccomplished by providing a coating composition prepared with a mixtureof

(a) 20 to 80 mole % of a compound having the general formula: ##STR3##where R₁ represents the group formed by removal of the two carboxylgroups from a cycloaliphatic and/or aromatic dicarboxylic acid having 8to 20 carbon atoms and R₂ and R₃ may be the same or different andrepresent groups formed by the removal of the two hydroxyl groups from adihydroxy alcohol having 2 to .[.12.]. .Iadd.6 .Iaddend.carbon atoms,and m is an integer of 1 to 3, and of

(b) 80 to 20 mole % of a compound having the general formula: ##STR4##where R₄ represents the group formed by the removal of the two carboxylgroups from an aliphatic dicarboxylic acid having 2 to 12 carbon atoms,and R₅ and R₆ may be the same or different and represent groups formedby the removal of the two hydroxyl groups from a dihydroxy alcoholhaving 2 to .[.12.]. .Iadd.6 .Iaddend.carbon atoms, and n is an integerof 1 to 3.

By high solids coating compositions are to be understood herecompositions having a solids content of at least 70% by weight andpreferably at least 80% by weight. The solids content is determined inconformity with ASTM method D 1644-59 upon heating for 1 hour at 105° C.

The mixture of ester diols according to the invention comprises (a) anester diol which may be formed from one or more cycloaliphatic oraromatic dicarboxylic acids, an anhydride or an alkyl ester thereof, thealkyl group generally containing 1 to 4 carbon atoms, and from one ormore diols and/or corresponding epoxy compounds. Any suitabledicarboxylic acid or derivative thereof may be used such as, forexample, tetrahydrophthalic acid, tetrahydrophthalic anhydride,endomethylene tetrahydrophthalic acid, hexachloroendomethylenetetrahydrophthalic acid, hexahydrophthalic acid, phthalic acid,p-carboxymethyl benzoic acid, dichlorophthalic acid, tetrachlorophthalicacid, dimethyl terephthalate, naphthalene-2,6-dicarboxylic acid,biphenyl-0,0'-dicarboxylic acid and the like. One or more dicarboxylicacids having 8 to 10 carbon atoms, for example, isophthalic acid andterephthalic acid are preferred. Any suitable diols and/or epoxycompounds may be used such as, for example, ethylene glycol, ethyleneoxide, propane-1,2-diol, propane-1,3-diol, propylene oxide, 2,2-dimethylpropane diol, butane-1,2-diol, butane-1,3-diol, butane-1,4-diol,butylene oxide, hexane-1,6-diol, diethylene glycol, triethylene glycol,dipropylene glycol, .[.2-ethyl hexane-1,6-diol, 2,2,4-trimethylpentane-1,3-diol, 2,2,4-trimethyl hexane-1,6-diol, octane-1,8-diol.].and the like. It is preferred that a diol having 2 to .[.9.]. .Iadd.5.Iaddend.carbon atoms should be used. The afore-described ester diolswill hereinafter be referred to as "cyclic ester diol".

The mixture of ester diols according to the invention also comprises (b)an ester diol which may be formed from one or more aliphaticdicarboxylic acids, an anhydride or an alkyl ester thereof, the alkylgroup generally containing 1 to 4 carbon atoms, and from one or morediols and/or corresponding epoxy compounds. Any suitable aliphaticdicarboxylic acid or derivative may be used for example, oxalic acid,malonic acid, succinic acid, succinic anhydride, glutaric acid, adipicacid, azelaic acid, sebacic acid, maleic acid, maleic anhydride, fumaricacid, itaconic acid, citraconic acid and the like. It is preferred thatuse should be made of one or more aliphatic dicarboxylic acids with 2 to10 carbon atoms, more particularly dicarboxylic acids having 4 to 6carbon atoms, which acids may or may not be ethylenically unsaturated,for instance, maleic acid and/or adipic acid. The diols and/or epoxycompounds to be used in the preparation of this type of ester diol maybe the same as the ones used in the preparation of the cyclic esterdiol, but there is no absolute need for that. It is preferred that useshould be made of a diol having 2 to .[.9.]. .Iadd.5 .Iaddend.carbonatoms. The above-envisaged type of ester diol will hereinafter bereferred to as "aliphatic ester diol".

The number average molecular weight of the cyclic and the aliphaticester diols is generally in the range of 254 to 2000 and 178 to 2000,respectively, and preferably in the range of 254 to 550 and 178 to 550,respectively. In general, the mixture of ester diols according to theinvention forms more than 60% by weight of the binder (i.e., notincluding the curing agent of the coating composition), and preferablyat least 75% by weight.

The ester diols to be used according to the invention may be prepared inany suitable manner. For example, one or more diols and/or epoxycompounds may be brought into reaction with one or more dicarboxylicacids, an anhydride and/or an alkyl ester thereof in a molar ratio ofthe order of 2:1. Alternatively, a dicarboxylic anhydride may first bereacted with a diol in a molar ratio of the order of 1:1, after whichthe resulting reaction product is reacted with an epoxy compound andpreferably in a molar ratio of the order of 1:1. The esterificationreactions take place at an elevated temperature, for instance, at 115°to 250° C., in the presence, if desired, of one or more organicsolvents, such as toluene or xylene. It is preferred that the reactionshould be so carried out that the average number of ester groups permolecule of the prepared ester diol is in the range of 2 to 4 (m or n 1to 2). The reaction will generally be carried out in the presence of anesterification catalyst of a usual concentration. The catalyst may beany of the known catalysts and may, for instance, be an acid catalystsuch as p-toluene sulphonic acid, a basic compound such as an amine orcompounds such as zinc oxide, tetraisopropyl orthotitanate and triphenylbenzyl phosphonium chloride.

According to the invention the molar ratio of the cyclic ester diol tothe aliphatic ester diol is generally between 8:2 and 2:8, andpreferably between 3:1 and 1:3, and more particularly between 2:1 and1:2.

The ester diols may be intermixed in any suitable manner; for instance,by first separately preparing the ester diols and subsequentlyintermixing them. Another suitable method consists in preparing one ofthe ester diols in the presence of the other ester diol or ester diols.

Depending on the method used for preparing the ester diols, otheresterification products may have formed in small amounts and be presentin the ester diols according to the invention. Such additionalesterification products usually are the higher molecular reactionproducts of the employed dicarboxylic acids and diols or derivatives ofthese compounds, for instance, esterification products having 7 to 10ester groups. As a rule, the ester diols according to the inventioncontain not more than about 5% by weight and often less than 1% byweight of such higher molecular esterification products.

As curing agent for the mixture of ester diols according to theinvention there may be used any curing agent suitable for curing acompound containing hydroxyl groups. Suitable curing agents generallyinclude N-methylol groups- and/or N-methylol ether groups-containingamino resins obtained by reacting an aldehyde, such as formaldehyde,with a compound containing amino groups or amido groups, such asmelamine, urea, N,N'-ethylene urea, dicyandiamide and benzoguanamine;for the preparation of such compounds, see Houben-Weyl, Methoden derorganischen Chemie, Band 14/2, pp. 319-371 (1963). It is preferred thatthe afore-described compounds should be entirely or partly etherifiedwith alcohols having 1 to 6 carbon atoms, for instance, with methanol,ethanol, n-propanol, isopropanol, n-butanol, isobutanol, amyl alcohol,hexanol or mixtures of the alcohols referred to above. Particularly, useis made of a methylol melamine containing 4 to 6 methylol groups permolecule of melamine, at least 3 methylol groups being etherified withmethanol, ethanol and preferably with butanol, or a butanol-etherifiedcondensation product of formaldehyde and N,N'-ethylene diurea. Moreparticularly, use is made of a hexalkoxymethyl melamine whose alkoxygroups contain 1 to 4 carbon atoms. Instead of or besides theabove-described curing agents other suitable agents may be used, such asblocked or non-blocked polyisocyanates. The curing agent is generallyused in such an amount that the molar ratio of the hydroxyl groups ofthe ester diol mixture to the reactive groups of the curing agent isapproximately between about 0.7 and 1.5 and preferably between 0.8 and1.3.

The coating composition may further contain usual auxiliary materialsand additives, such as pigment dispersing agents, thixotropic agents orother means to influence the rheological properties, and colorants,solvents and accelerators for the curing reaction, for instance, acidcompounds such as paratoluene sulphonic acid or blocked productsthereof.

In any case the coating composition contains one or more pigments in atotal amount of at least 30% by weight, calculated on the total solidscontent of the coating composition. Suitable pigments include the usualkinds, namely acid, neutral or basic pigments which may be of an organicor an inorganic nature. If desired, the pigments may have beenpre-treated to modify the properties. As examples of suitable pigmentsmay be mentioned titanium dioxide, iron oxide red, carbon black andphthalocyanin pigments. By pigments are also to be understood heremetallic pigments such as those of aluminum and stainless steel. Thecoating composition ready for use generally has a viscosity not higherthan 20 poises, and preferably 0.5 to 10 poises.

The coating composition may be applied to the substrate in any desirableway, for instance,, by roller coating, spraying, brushing, sprinkling,flow-coating, dipping or electrostatic spraying.

Further, the coating composition may be cured or baked in the usualmanner, for instance, at ambient temperature or at the usualtemperatures between, say, 100° and 160° C., in a residence time of 20to 60 minutes in a baking oven.

Preparation of Ester Diols Method A

The following materials were charged into a reactor equipped with astirrer, a thermometer and a condenser: 1461 grams of adipic acid, 3044grams of propane-1,2-diol, 4 grams of zinc oxide. The mixture was heatedto a temperature slightly above 150° C., upon which the water formed inthe esterification reaction began to flow over. During the reaction 360grams of water were distilled off, the temperature rising to 180° C.After the temperature had subsequently been decreased to 90° C., theexcess of propane-1,2-diol (1522 grams) was distilled off in vacuo. Theester prepared contained on an average 2.5 ester groups per molecule(n=1.25) and will hereinafter be referred to asdi(propane-1,2-diol)adipate.

Method B

Into a reactor provided with a stirrer, a thermometer and a condenserthere were successively charged 1942 grams of dimethyl terephthalate,3044 grams of propane-1,2-diol and 2.5 grams of tetraisopropylorthotitanate. The mixture was heated to a temperature slightly above150° C., upon which the methanol formed in the trans-esterificationreaction began to flow over. During the reaction 641 grams of methanolwere distilled off, the temperature rising to 180° C. After thetemperature had subsequently been decreased to 90° C., the excess ofpropane-1,2-diol (1522 grams) was distilled off in vacuo. The esterprepared contained on an average 3.0 ester groups per molecule (m=1.5)and is hereinafter referred to as tri(propane-1,2-diol)terephthalate.

Method C

Into a reactor provided with a stirrer, a thermometer, a refluxcondenser and a dropping funnel there were charged 1661 grams ofisophthalic acid. The reactor was subsequently heated to 150° C., afterwhich a mixture of 1276 grams of propylene oxide and 3 grams oftriphenyl benzyl phosphonium chloride were added so slowly that a steadyreflux at 150° C. was maintained. After the entire mixture had beenadded, the temperature was for one more hour kept at 150° C. Aftercompletion of the reaction the small excess of propylene oxide wasremoved in vacuo. The ester prepared had on an average 2.4 ester groupsper molecule (m=1.2) and is hereinafter referred to asdi(propane-1,2-diol)isophthalate.

Method D

Into a reactor equipped with a stirrer, a thermometer, a refluxcondenser and a dropping funnel there were charged 1481 grams ofphthalic anhydride and 761 grams of propane-1,2-diol. The mixture washeated to 120° C., after which the reactor was cooled, so that therising temperature of the contents as a result of reaction heat could bekept below 180° C. After the temperature had dropped to 150° C., amixture of 638 grams of propylene oxide and 1.5 grams of triphenylbenzyl phosphonium chloride was added so slowly that a steady reflux at150° C. was maintained. After the entire mixture had been added, thetemperature was for one more hour kept at 150° C. After completion ofthe reaction, the small excess of propylene oxide was removed in vacuo.The ester prepared contained on an average 2.4 ester groups per molecule(m=1,2) and is referred to hereinafter as di(propane-1,2-diol)phthalate.

In the following comparative examples and the other examples, which arenot to be interpreted as limiting the scope of the present invention,the Persoz hardness was measured and expressed in seconds. Theflexibility was determined with the aid of the "Falling-weight" tester(Erichsen - type 304) in accordance with ASTM D 2794-69, using a weightof 0.908 kg measuring 15.9 mm in diameter and a dropping opening of 16.3mm, the value obtained being expressed in kg-cm. In accordance with thismethod the values were determined both for the coated side and the backof the steel test panel (Bonder 120). Moreover, the conical mandrel testwas carried out, its results being expressed in mm. An acceptableminimum value of the hardness is about 200 seconds. An acceptableminimum value of the flexibility is of the order of 35 kg-cm, thehighest value to be measured being 85 kg-cm. The conical mandrel test(carried out in accordance with ASTM D 522-41) gives a value below thelower measuring value 1 in the case of very flexible coatings; a valueof 104 in this test is indicative of the coating being very brittle. Thegloss was determined at 60° and at 20° (ASTM D-523). A gloss value of 90at 60° is considered very high. A gloss value above 80 at 20° is alsoregarded as high. The values of the measured properties are listed inTable 1.

The sprayable compositions described in the comparative examples and inthe other examples all have a viscosity of 25 seconds at 20° C. (Fordcup No. 4). The resulting coating (after baking) had the thickness givenin Table 1.

EXAMPLES Comparative Example 1

The following components were homogeneously mixed:

tri(propane-1,2-diol)terephthalate (prepared by method B): 280 g

hexamethoxymethyl melamine: 130 g

20% solution of p-toluene sulphonic acid in isopropanol: 6 g

This mixture was diluted to spray viscosity by combining it with 68grams of a mixture of equal parts by weight of xylene and ethyl glycolacetate. The resulting unpigmented coating composition was applied to asteel panel treated with zinc phosphate (Bonder 120) and cured for 30minutes at a temperature of 130° C. The coating obtained had a goodhardness and was not brittle (see also Table 1).

Comparative Example 2

To find out the influence of the presence of a pigment in the propertiesof the coating a sprayable coating composition having the followingconstituents:

tri(propane-1,2-diol)terephthalate (prepared by method B): 280 g

hexamethoxymethyl melamine: 130 g

20% solution of p-toluene sulphonic acid in isopropanol: 10 g

titanium dioxide: 282 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 117g

was applied and tested in the same manner as described in ComparativeExample 1. It was found that, although the baked pigmented coating had agood hardness, it was very brittle (see also Table 1).

Comparative Example 3

A pigmented coating composition prepared from an aliphatic ester diolwas tested in the same way as indicated in Comparative Example 1.

The coating composition was made up of the following constituents:

di(propane-1,2-diol)adipate (prepared by method A): 260 g

hexamethoxymethyl melamine: 130 g

20% solution of p-toluene sulphonic acid in isopropanol: 10 g

titanium dioxide: 267 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 89 g

It was found that, although the baked, pigmented coating had a highflexibility, its hardness was insufficient (see also Table 1).

Comparative Example 4

Into a reactor provided with a stirrer, a thermometer, a refluxcondenser and a dropping funnel there were charged 830 grams ofterephthalic acid and 1095 grams of adipic acid. The mixture was heatedto a temperature of 150° C., after which a mixture of 1600 grams ofpropylene oxide and 4 grams of triphenylbenzylphosphonium chloride wasadded so slowly that a steady reflux at 150° C. was maintained. Afterthe entire mixture had been added, the temperature was kept at 150° C.for one more hour. At conclusion of the reaction the small excess ofpropylene oxide was removed in vacuo. The ester obtained had on anaverage 3 ester groups per molecule.

A coating composition prepared from the afore-described ester diol wastested in the same way as described in Comparative Example 1. Thecoating composition was made up as follows:

ester diol: 236 g

hexamethoxymethyl melamine: 114 g

20% solution of p-toluene sulphonic acid in isopropanol: 9 g

titanium dioxide: 240 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 89 g

It was found that, although the baked, pigmented coating had a highflexibility, its hardness was insufficient (see also Table 1).

EXAMPLE 1

The following components were homogeneously mixed:

tri(propane-1,2-diol)terephthalate (prepared by method B): 98 g

di(propane-1,2-diol)adipate (prepared by method A): 138 g

hexamethoxymethyl melamine: 114 g

20% solution of p-toluene sulphonic acid in isopropanol: 9 g

titanium dioxide: 240 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 90 g

The sprayable composition was applied to a steel panel treated with zincphosphate (Bonder 120) and cured for 30 minutes at a temperature of 130°C. The properties of the baked coating are listed in Table 1.

EXAMPLE 2

Example 1 was repeated, except that for the preparation of the coatingcomposition use was made of 98 grams of di(propane-1,2-diol)isophthalateinstead of the 98 grams of tri(propane-1,2-diol)terephthalate. Theisophthalate was prepared by method C. The coating composition wasapplied and tested as indicated in Example 1. The properties of thebaked coating are listed in Table 1.

EXAMPLE 3

Example 1 was repeated, except that for the preparation of the coatingcomposition use was made of 98 grams of di(propane-1,2-diol)phthalateinstead of the 98 grams of tri(propane-1,2-diol)-terephthalate. Thephthalate was prepared by method D. The coating composition was appliedand tested as indicated in Example 1. The properties of the bakedcoating are mentioned in Table 1.

EXAMPLE 4

The following components were homogeneously intermixed:

di(propane-1,2-dioltetrahydrophthalate (prepared analogously to methodD; m=1.25): 133 g

di(hexane-1,6-diol)maleinate (prepared analogously to method A; n=1.25):111 g

hexamethoxymethyl melamine: 106 g

20% solution of p-toluene sulphonic acid in isopropanol: 9 g

titanium dioxide: 240 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 110g

The sprayable composition was applied and tested as indicated inExample 1. The properties of the baked coating are listed in Table 1.

EXAMPLE 5

The following components were homogeneously intermixed:

di(propane-1,2-diol)isophthalate (prepared by method C): 123 g

di(hexane-1,6-diol)maleinate (prepared analogously to method A; n=1.25):121 g

hexamethoxymethyl melamine: 106 g

20% solution of p-toluene sulphonic acid in isopropanol: 9 g

titanium dioxide: 240 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 100g

The sprayable composition was applied and tested in the same way asindicated in Example 1. The properties of the baked coating are listedin Table 1.

.[.EXAMPLE 6.].

.[.The following components were homogeneously intermixed: .].

.[.di(2,2,4-trimethyl pentane-1,3-diol)isophthalate (preparedanalogously to method A; m=1.2): 180 g .].

.[.di(2,2,4-trimethyl pentane-1,3-diol)adipate (prepared by using theprocedure of method A; n=1.25): 90 g .].

.[.hexamethoxymethyl melamine: 95 g .].

.[.20% solution of p-toluene sulphonic acid in isopropanol: 9 g.].

.[.titanium dioxide: 240 g.].

.[.mixture of equal parts by weight of xylene and ethylglycol acetate:92 g.].

.[.The sprayable composition was applied and tested as indicated inExample 1. The properties of the baked coating are listed in Table 1..].

EXAMPLE .[.7.]. .Iadd.6 .Iaddend.

The following components were homogeneously intermixed:

di(neopentyl glycol) isophthalate (prepared analogously to method A;m=1.3); 170 g

di(neopentyl glycol)adipate (prepared analogously to method A; n=1.2):85 g

hexamethoxymethyl melamine: 110 g

20% solution of p-toluene sulphonic acid in isopropanol: 9 g

titanium dioxide: 240 g

mixture of equal parts by weight of xylene and ethylglycol acetate: 96 g

The sprayable composition was applied and tested as indicated inExample 1. The properties of the baked coating are listed in Table 1.

.[.EXAMPLE 8.].

.[.Example 7 was repeated, except that for the preparation of thecoating composition use was made of 85 grams of di(2,2,4-trimethylpentane-1,3-diol)adipate instead of the 85 grams of di(neopentylglycol)adipate. The adipate was prepared by method A (n=1.25). Thecoating composition was applied and tested as indicated in Example 1.The properties of the baked coating are listed in Table 1..].

EXAMPLE .[.9.]. .Iadd.7 .Iaddend.

Example .[.7.]. .Iadd.6 .Iaddend.was repeated, except that for thepreparation of the coating composition both the di(neopentylglycol)isophthalate and the di(neopentyl glycol)adipate were used inamounts of 128 grams. The coating composition was applied and tested inthe same way as indicated in Example 1. The properties are listed inTable 1.

.[.EXAMPLE 10.].

.[.Example 8 was repeated, except that for the preparation of thecoating composition both the di(2,2,4-trimethyl pentane-1,3-diol)adipateand the di(neopentyl glycol)isophthalate were used in amounts of 128grams. The coating composition was applied and tested as indicated inExample 1. The properties are listed in Table 1..].

.[.EXAMPLE 11.].

.[.Example 7 was repeated, except that for the preparation of thecoating composition use was made of 170 grams of di(2,2,4-trimethylpentane-1,3-diol)isophthalate instead of the 170 grams of di(neopentylglycol)isophthalate. The coating composition was applied and tested asindicated in Example 1. The properties are listed in Table 1..].

                                      TABLE 1                                     __________________________________________________________________________                          FALLING-WEIGHT                                          COMPAR-                                                                              COATING PERSOZ TEST (KG-CM)                                                                             CONICAL                                      ATIVE  THICKNESS                                                                             HARDNESS                                                                             COATING    MANDREL                                                                              GLOSS                                 EXAMPLE                                                                              (μm) (sec.) SIDE  BACK TEST (mm)                                                                            60°                                                                        20°                        __________________________________________________________________________    1      40      340    >85   >85  <1     --  --                                2      40      310     14   <2   >104   99  75                                3      45      82     >85   >85  <1     93  70                                4      40      90     >85   >85  <1     91  70                                EXAMPLE                                                                       1      40      255    >85   >85  <1     97  82                                2      40      250    >85   >85  <1     95  75                                3      25      240    >85   >85  <1     97  82                                4      35      220    >85   >85  <1     96  86                                5      40      260    >85   >85  <1     97  89                                .[.6.].                                                                              .[.40.].                                                                              .[.280.].                                                                            .[.>85.].                                                                           .[.>85.].                                                                          .[.< 1.].                                                                            .[.92.].                                                                          .[.85.].                          .[.7.]..Iadd.6.Iaddend.                                                              40      >300   >85   >85  <1     96  90                                .[.8.].                                                                              .[.40.].                                                                              .[.>300.].                                                                           .[.>85.].                                                                           .[.>85.].                                                                          .[.<1.].                                                                             .[.98.].                                                                          .[.91.].                          .[.9.]..Iadd.7.Iaddend.                                                              40      >300   >85   >85  <1     93  85                                .[.10.].                                                                             .[.40.].                                                                              .[.>300.].                                                                           .[.>85.].                                                                           .[.>85.].                                                                          .[.<1.].                                                                             .[.96.].                                                                          .[.88.].                          .[.11.].                                                                             .[.40.].                                                                              .[.>300.].                                                                           .[.>85.].                                                                           .[.>85.].                                                                          .[.<1.].                                                                              .[.95.].                                                                         .[.88.].                          __________________________________________________________________________

Although the invention has been described in detail for the purpose ofillustration, it is to be understood that such detail is solely for thatpurpose and that variations can be made therein by those skilled in theart without departing from the spirit and scope of the invention exceptas it may be limited by the claims.

What is claimed is:
 1. A high solids pigmented coating compositionprepared from a blend of an ester diol as binder and a curing agent forthe binder, characterized in that (1) the ester diol is a mixture of(a)20-80 mole % of an ester diol having the general formula: ##STR5## whereR₁ represents the group formed by abstraction of the carboxyl groupsfrom a cycloaliphatic and/or aromatic dicarboxylic acid having 8 to 20carbon atoms and R₂ and R₃ may be the same or different and representgroups formed by abstraction of the two hydroxyl groups from a divalentalcohol having 2 to .[.12.]. .Iadd.6 .Iaddend.carbon atoms, and m is anumber of 1-3, and (b) 80-20 mole % of an ester diol having the generalformula: ##STR6## where R₄ represents the group formed by abstraction ofthe two carboxyl groups from an aliphatic dicarboxylic acid having 2 to12 carbon atoms, and R₅ and R₆ may be the same or different andrepresent groups formed by abstraction of the two hydroxyl groups from adivalent alcohol having 2 to .[.12.]. .Iadd.6 .Iaddend.carbon atoms, andn is a number of 1-3, (2) the curing agent for the binder is anaminoplast, and (3) the amount of pigment in said coating composition isat least 30% by weight, based on the total solids content.
 2. Thecoating composition of claim 1 characterized in that the molar ratio ofthe ester diols is between 3:1 and 1:3.
 3. The coating composition ofclaim 1 characterized in that the molar ratio of the ester diols isbetween 2:1 and 1:2.
 4. The coating composition of claim 1 characterizedin that one of the ester diols is formed from a cycloaliphatic oraromatic dicarboxylic acid containing 8 to 10 carbon atoms and a diolcontaining 2 to .[.9.]. .Iadd.6 .Iaddend.carbon atoms.
 5. The coatingcomposition of claim 1 characterized in that one of the ester diols isformed from an aliphatic dicarboxylic acid containing 2 to 10 carbonatoms and a diol containing 2 to .[.9.]. .Iadd.6 .Iaddend.carbon atoms.6. The coating composition of claim 1 characterized in that the molarratio of the hydroxyl groups of the ester diol mixture to the reactivegroups of the curing agent is between about 0.7 and about 1.5.
 7. Theprocess for the preparation of a coating composition having a highsolids content characterized in that it comprises the preparation of thecoating composition of claim
 1. 8. The coating composition of claim 1wherein said curing agent for the binder is a methylol melaminecontaining 4 to 6 methylol groups per molecule of melamine, at least 3of said methylol groups being etherified with an alcohol selected fromthe group consisting of methanol, ethanol, and butanol.
 9. The coatingcomposition of claim 1 wherein said curing agent for the binder is anN-methylol group-and/or N-methylol ether group- containing amino resinformed by reacting an aldehyde with a compound containing amino groupsor amido groups. .Iadd.
 10. A high solids pigmented coating compositionprepared from a blend of an ester diol as binder and a curing agent forthe binder, characterized in that (1) the ester diol is a mixture of (a)20-80 mole % of an ester diol having the general formula:##STR7##.Iaddend. where R₁ represents the group formed by abstraction ofthe carboxyl groups from a cycloaliphatic and/or aromatic dicarboxylicacid having 8 to 20 carbon atoms and R₂ and R₃ represent groups formedby abstraction of the two hydroxyl groups from neopentyl glycol, and mis a number of 1-3, and (b) 80-20 mole % of an ester diol having thegeneral formula: ##STR8## where R₄ represents the group formed byabstraction of the two carboxyl groups from an aliphatic dicarboxylicacid having 2 to 12 carbon atoms, and R₅ and R₆ represent groups formedby abstraction of the two hydroxyl groups from neopentyl glycol, and nis a number of 1-3,(2) the curing agent for the binder is an aminoplast,and (3) the amount of pigment in said coating composition is at least30% by weight, based on the total solids content. .Iadd.
 11. The coatingcomposition of claim 10, characterized in that the molar ratio of theester diols is between 3:1 and 1:3. .Iaddend. .Iadd.12. The coatingcomposition of claim 10, characterized in that the molar ratio of theester diols is between 2:1 and 1:2. .Iaddend. .Iadd.13. The coatingcomposition of claim 10, characterized in that one of the ester diols isformed from a cycloaliphatic or aromatic dicarboxylic acid containing 8to 10 carbon atoms and neopentyl glycol. .Iaddend. .Iadd.14. The coatingcomposition of claim 10, characterized in that one of the ester diols isformed from an aliphatic dicarboxylic acid containing 2 to 10 carbonatoms and neopentyl glycol. .Iaddend. .Iadd.15. The coating compositionof claim 10, characterized in that the molar ratio of the hydroxylgroups of the ester diol mixture to the reactive groups of the curingagent is between 0.7 and about 1.5. .Iaddend. .Iadd.16. The process forthe preparation of a coating composition having a high solids contentcharacterized in that it comprises the preparation of the coatingcomposition of claim
 10. .Iaddend. .Iadd.17. The coating composition ofclaim 10, wherein said curing agent for the binder is a methylolmelamine containing 4 to 6 methylol groups per molecule of melamine, atleast 3 of said methylol groups being etherified with an alcoholselected from the group consisting of methanol, ethanol, and butanol..Iaddend. .Iadd.18. The coating composition of claim 10, wherein saidcuring agent for the binder is an N-methylol group- and/or N-methylolether group-containing amino resin formed by reacting an aldehyde with acompound containing amino groups or amido groups.